Twitter has warned that wishing president Donald Trump dead is a breach of its rules, and could result in suspension.
The US president is in hospital receiving an experimental antibody treatment after testing positive for coronavirus on Friday.
Mr Trump received an influx of messages of support on the platform – but a small minority instead wished the worst upon him.
The social media company confirmed that tweets wishing anybody dead would be removed from the platform.
It said: “Tweets that wish or hope for death, serious bodily harm or fatal disease against *anyone* are not allowed and will need to be removed.”
It added that the removal of tweets would not always lead to suspension.
According to Twitter’s rules on abusive behaviour, the company does not tolerate content that “wishes, hopes or expresses a desire for death, serious bodily harm or fatal disease against an individual or group of people”.
The policy gives the example of “hoping that someone dies as a result of a serious disease”.
Twitter says it considers a number of factors in determining the penalty for someone breaching the rules, including “the severity of the violation and an individual’s previous record”.
Penalties may include serving a period of time in ‘read only’ mode and, in serious cases, permanent suspension.
Mr Trump was airlifted to hospital less than 24 hours after his Covid-19 diagnosis.
He was taken to the Walter Reed National Military Medical Centre on Friday and is expected to remain there for “a few days”.
A White House spokeswoman stressed that the hospital stay was “out of an abundance of caution” and that the 74-year-old would work from the hospital’s presidential suite, which is equipped to allow him to continue his official duties.
Boris Johnson said he is sure the president will “come through” his treatment “very well”.
Speaking to reporters on Saturday morning, Mr Johnson said he rang the White House on Friday night and added: “I think obviously everybody’s wishing him and Melania the very best and hoping that they recover speedily and I’ve no doubt that he will, he’ll make a very strong recovery.”